Yep, DG is probably about the best you'll do OTC. You can polish by hand, but you will not obtain the same results as you would with a machine (DA or rotary). This rabbit hole can go pretty deep, pretty quickly. If you're just maintaining your own cars, the probably something like the Porter-Cable 7424 and some pads would work. Although I am smitten with my Flex 3401, but that's about double the cost of the
PC.